Learn Hardcore Korean: chinguege mesijireul bonaesseoyo.

-에게 marks the recipient/indirect object (to someone). -한테 is the more casual/spoken equivalent; both are fine with people or animals. For honored recipients, use -께.

Examples:
- 친구에게 메시지를 보냈어요.
- 친구한테 메시지 보냈어요. (more casual)
- 선생님께 메시지를 보냈습니다. (honorific/formal)

Why is there no subject? Who sent the message?

Korean often drops subjects when they’re clear from context. In most everyday contexts, the omitted subject is “I.”

To make it explicit, you can say: 제가 친구에게 메시지를 보냈어요. (I sent a message to my friend.)
Topic style: 저는 친구에게 메시지를 보냈어요. (As for me, I sent a message to my friend.)

Why does 메시지를 take 를?

를/을 marks the direct object. 메시지 is the thing being sent (direct object), so it takes the object marker. Use 를 after a vowel-ending noun and 을 after a consonant-ending noun.

메시지를 보냈어요.
편지를 보냈어요.
사진을 보냈어요.

Can I change the word order?

Yes. Because particles mark roles, word order is flexible, though the default is recipient + object + verb.

Default: 친구에게 메시지를 보냈어요.
Also fine: 메시지를 친구에게 보냈어요. If you drop particles in casual speech, prefer the default order to avoid ambiguity: 친구한테 메시지 보냈어요.

Is 메시지 the correct spelling? Why do I also see 메세지?

The standard spelling is 메시지 (not 메세지). You’ll see 메세지 informally, but it’s nonstandard. For “text message,” people commonly say 문자:

친구한테 문자 보냈어요. (I texted my friend.)

How is 보냈어요 formed?

Dictionary form: 보내다 (to send).

Past polite: 보내다 + 았어요 (because the stem has the ㅏ/ㅗ family vowel) → 보내았어요 → contracted to 보냈어요.
Other forms:
- Present polite: 보내요
- Future: 보낼 거예요
- Formal past: 보냈습니다
- Casual past: 보냈어

How do you pronounce this naturally?

보냈어요 is pronounced roughly “bo-nae-sseo-yo” ([보내써요], because ㅆ links to the next syllable).
메시지를: “me-si-ji-reul”
친구에게: “chin-gu-e-ge” Analogy: 있어요 → 이써요 by the same linking.

Can I drop the particles (를/을, 에게) in conversation?

Often, yes—especially 를/을. In casual speech:

친구한테 메시지 보냈어요.
친구한테 문자 보냈어. In careful speech or writing, keep them for clarity.

How do I say “to my friend,” “to a friend,” or “to my friends”?

Explicit “my friend”: 제 친구에게 메시지를 보냈어요. (polite) / 내 친구한테 (casual)
Indefinite “a friend”: 어떤 친구에게 메시지를 보냈어요. or 친구 한 명에게…
Plural: 친구들에게 메시지를 보냈어요.

How do I make it more honorific or humble?

Use -께 for respected recipients and optionally add the humble auxiliary -드리다 when the action benefits them.

선생님께 메시지를 보냈습니다.
선생님께 메시지를 보내 드렸습니다. Using -께 with 친구 is odd unless you’re being playful/ironic.

How do I ask or negate this sentence?

Question (polite): 친구에게 메시지 보냈어요? / Formal: 보냈습니까?
Negative: 친구에게 메시지를 안 보냈어요. or 보내지 않았어요. Both negatives are correct; 안 + verb is more common in speech.

Can I use -에 instead of -에게?

Not with people. 친구에 is unnatural for “to a friend.” Use -에게/-한테 for people/animals. With places or institutions, -에 is normal:

회사에 이메일을 보냈어요. (to the company)
With institutions, 회사에게 is sometimes used, but 회사에 is more common.

What’s the difference between -에게/-한테 and -에게서/-한테서?

-에게 / -한테: to someone (recipient)
-에게서 / -한테서: from someone (source) Examples:
친구한테서 메시지를 받았어요. (I received a message from my friend.)
Don’t say 친구에게서 메시지를 보냈어요 for “sent to”—that’s incorrect.

How can I add “only” or “also,” or add a contrastive topic?

Attach particles after the recipient phrase:

Only: 친구에게만 메시지를 보냈어요.
Also: 친구에게도 메시지를 보냈어요.
Contrast/topic: 친구에겐 메시지를 보냈어요. (에게 + 는 → 에겐)

Why is there no space before 에게 and 를?

Case particles (에게, 한테, 에, 을/를, 은/는, 이/가, etc.) attach directly to the noun with no space:

친구에게, 메시지를 are correct.

Can I swap in other things I might send?

Yes—keep the particles and change the noun:

친구에게 편지를 보냈어요. (a letter)
친구에게 이메일을 보냈어요. (an email)
친구에게 사진을 보냈어요. (a photo)
친구에게 파일을 보냈어요. (a file)